The invention relates to a dilatation catheter according to the preamble of independent Patent Claim 1. Catheters of this generic type were first developed by A. Gruntzig for percutaneous transluminal recanalization of chronic arterial occlusions and have since then been steadily increasing in importance. The catheter system used for this consists generally of a guide wire, a dilatation catheter with at least a two-lumen shaft, and a dilatation balloon arranged distally on the shaft, and also a guide catheter. The guide wire and, on it, the dilatation catheter is pushed through the guide catheter until the dilatation balloon is situated in the stricture. The balloon is now dilated with liquid, and the arteriosclerotic material is pressed radially against and into the vessel wall so that, after removal of the catheter, the vessel fluid can again pass through the treated area.
The shaft of the dilatation catheter usually consists essentially of two coaxial tube pieces, in which respect the inner tube receives the guide wire, and an intermediate space between the two tube pieces forms the lumen for the liquid for dilating the balloon. When the balloon is pushed into severe strictures, as a result of the comparatively high axial forces, the balloon and the tube connected to it are compressed, which makes the introduction of the balloon into the stricture difficult. In order to avoid this, as stiff a shaft as possible would be desirable. In contrast, if the stricture lies downstream of a vessel curve, then the shaft should be as flexible as possible in the front area, so that it can follow the vessel curve with as little friction as possible.
In order to overcome this difficulty, a two-lumen dilatation catheter has been disclosed by EP-A-0,277,368, in which the catheter the shaft is made up of several areas of different stiffness. Thus, optimum flexibility and stability should be achieved at different points along the catheter. For this purpose, shaft portions made of different materials are produced, and these are connected to one another thermoplastically.
A dilatation balloon is also known in which the two coaxial tube pieces of the shaft are connected directly behind the balloon with webs. These webs transmit the axial shear force from the outer tube to the inner tube and should prevent the abovementioned compression of the shaft during the treatment of severely stenosed vessels. Such webs make the production of the catheter considerably more difficult and expensive and they narrow the lumen for the passage of the pressure liquid.